Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive.

Example:

Given nums = [-2, 0, 3, -5, 2, -1]sumRange(0, 2) -> 1sumRange(2, 5) -> -1sumRange(0, 5) -> -3

 

Note:

1. You may assume that the array does not change.
2. There are many calls to sumRange function.

前缀和的应用，很简单。

class NumArray {public:    int n;    vector
     
       s;    NumArray(vector
      
        &nums) {        n = nums.size();        if(n==0)return;                s.push_back(nums[0]);        for(int i=1;i
       
        j)return 0;        if(i==0) return s[j];        return s[j]-s[i-1];    }};// Your NumArray object will be instantiated and called as such:// NumArray numArray(nums);// numArray.sumRange(0, 1);// numArray.sumRange(1, 2);